Fate analysis of adult hippocampal progenitors in a murine model of fetal alcohol spectrum disorder (FASD)

The Fetal Alcohol Spectrum Disorders-An Overview of Experimental Models, Therapeutic Strategies, and Future Research Directions

Since the establishment of a clear link between maternal alcohol consumption during pregnancy and certain birth defects, the research into the treatment of FASD has become increasingly sophisticated. The field has begun to explore the possibility of intervening at different levels, and animal studies have provided valuable insights into the pathophysiology of the disease, forming the basis for implementing potential therapies with increasingly precise mechanisms. The recent reports suggest that compounds that reduce the severity of neurodevelopmental deficits, including glial cell function and myelination, and/or target oxidative stress and inflammation may be effective in treating FASD. Our goal in writing this article was to analyze and synthesize current experimental therapeutic interventions for FASD, elucidating their potential mechanisms of action, translational relevance, and implications for clinical application. This review exclusively focuses on animal models and the interventions used in these models to outline the current direction of research. We conclude that given the complexity of the underlying mechanisms, a multifactorial approach combining nutritional supplementation, pharmacotherapy, and behavioral techniques tailored to the stage and severity of the disease may be a promising avenue for further research in humans.

Altering Cell-Cell Interaction in Prenatal Alcohol Exposure Models: Insight on Cell-Adhesion Molecules During Brain Development

Alcohol exposure during pregnancy disrupts the development of the brain and produces long lasting behavioral and cognitive impairments collectively known as Fetal Alcohol Spectrum Disorders (FASDs). FASDs are characterized by alterations in learning, working memory, social behavior and executive function. A large body of literature using preclinical prenatal alcohol exposure models reports alcohol-induced changes in architecture and activity in specific brain regions affecting cognition. While multiple putative mechanisms of alcohol’s long-lasting effects on morphology and behavior have been investigated, an area that has received less attention is the effect of alcohol on cell adhesion molecules (CAMs). The embryo/fetal development represents a crucial period for Central Nervous System (CNS) development during which the cell-cell interaction plays an important role. CAMs play a critical role in neuronal migration and differentiation, synaptic organization and function which may be disrupted by alcohol. In this review, we summarize the physiological structure and role of CAMs involved in brain development, review the current literature on prenatal alcohol exposure effects on CAM function in different experimental models and pinpoint areas needed for future study to better understand how CAMs may mediate the morphological, sensory and behavioral outcomes in FASDs.

Functional and Structural Correlates of Impaired Enrichment-Mediated Adult Hippocampal Neurogenesis in a Mouse Model of Prenatal Alcohol Exposure

Background:

Fetal alcohol spectrum disorders (FASDs) are associated with a wide range of cognitive deficiencies.

Objective:

We previously found that gestational exposure to moderate levels of alcohol in mice throughout the 1st-2nd human trimester-equivalents for brain development results in profound impairment of the hippocampal neurogenic response to enriched environment (EE) in adulthood, without altering baseline neurogenesis rate under standard housing (SH). However, the functional and structural consequences of impaired EE-mediated neurogenesis in the context of prenatal alcohol exposure (PAE) have not been determined.

Results:

Here, we demonstrate that PAE-EE mice display impaired performance on a neurogenesis-dependent pattern discrimination task, broadened behavioral activation of the dentate gyrus, as assessed by expression of the immediate early gene, c-Fos, and impaired dendritic branching of adult-generated dentate granule cells (aDGCs).

Conclusions:

These studies further underscore the impact of moderate gestational alcohol exposure on adult hippocampal plasticity and support adult hippocampal neurogenesis as a potential therapeutic target to remediate certain neurological outcomes in FASD.

Moderate Prenatal Alcohol Exposure Impairs Visual-Spatial Discrimination in a Sex-Specific Manner: Effects of Testing Order and Difficulty on Learning Performance

BACKGROUND

Exposure to high levels of alcohol during development leads to alterations in neurogenesis and deficits in hippocampal-dependent learning. Evidence suggests that even more moderate alcohol consumption during pregnancy can have negative impacts on the cognitive function of offspring. Methods for assessing impairments differ greatly across species, complicating translation of preclinical findings into potential therapeutics. We have demonstrated the utility of a touchscreen operant measure for assessing hippocampal function in mice.

METHODS

Here, we integrated a well-established "drinking-in-the-dark" exposure model that produces reliable, but more moderate, levels of maternal intoxication with a trial-unique, delayed nonmatching-to-location (TUNL) task to examine the effects of prenatal alcohol exposure (PAE) on hippocampal-sensitive behavior directly analogous to those used in clinical assessment. PAE and SAC offspring mice were trained to touch a single visual stimulus ("sample phase") in one of 10 possible spatial locations (2 × 5 grid) in a touchscreen operant system. After a delay, animals were simultaneously presented with the original stimulus and a rewarded stimulus in a novel location ("choice phase"). PAE and saccharin (SAC) control mice were trained on a series of problems that systematically increased the difficulty by decreasing the separation between the sample and choice stimuli. Next, a separate cohort of PAE and SAC animals were given a brief training and then tested on a challenging variant where both the separation and delay varied with each trial.

RESULTS

We found that PAE mice were generally able to perform at levels similar to SAC control mice at progressively more difficult separations. When tested on the most difficult unpredictable variant immediately, PAE showed a sex-specific deficit with PAE females performing worse during long delays.

CONCLUSIONS

Taken together, these data demonstrate the utility of the TUNL task for examining PAE related alterations in hippocampal function and underline the need to examine sex-by-treatment interactions in these models.

Murine Models for the Study of Fetal Alcohol Spectrum Disorders: An Overview

Prenatal alcohol exposure is associated to different physical, behavioral, cognitive, and neurological impairments collectively known as fetal alcohol spectrum disorder. The underlying mechanisms of ethanol toxicity are not completely understood. Experimental studies during human pregnancy to identify new diagnostic biomarkers are difficult to carry out beyond genetic or epigenetic analyses in biological matrices. Therefore, animal models are a useful tool to study the teratogenic effects of alcohol on the central nervous system and analyze the benefits of promising therapies. Animal models of alcohol spectrum disorder allow the analysis of key variables such as amount, timing and frequency of ethanol consumption to describe the harmful effects of prenatal alcohol exposure. In this review, we aim to synthetize neurodevelopmental disabilities in rodent fetal alcohol spectrum disorder phenotypes, considering facial dysmorphology and fetal growth restriction. We examine the different neurodevelopmental stages based on the most consistently implicated epigenetic mechanisms, cell types and molecular pathways, and assess the advantages and disadvantages of murine models in the study of fetal alcohol spectrum disorder, the different routes of alcohol administration, and alcohol consumption patterns applied to rodents. Finally, we analyze a wide range of phenotypic features to identify fetal alcohol spectrum disorder phenotypes in murine models, exploring facial dysmorphology, neurodevelopmental deficits, and growth restriction, as well as the methodologies used to evaluate behavioral and anatomical alterations produced by prenatal alcohol exposure in rodents.

Resistance of Postnatal Hippocampal Neurogenesis to Alcohol Toxicity in a Third Trimester-Equivalent Mouse Model of Gestational Alcohol Exposure

BACKGROUND

The adult hippocampal dentate is comprised of both developmentally generated dentate granule cells (dDGCs) and adult-generated dentate granule cells (aDGCs), which play distinct roles in hippocampal information processing and network function. EtOH exposure throughout gestation in mouse impairs the neurogenic response to enriched environment (EE) in adulthood, although the basal rate of adult neurogenesis under standard housing (SH) is unaffected. Here, we tested whether the production and/or survival of either dDGCs or aDGCs are selectively impaired following exposure of mice to EtOH vapors during early postnatal development (human third trimester-equivalent), and whether this exposure paradigm leads to impairment of EE-mediated dentate neurogenesis in adulthood.

METHODS

All experiments were performed using NestinCreER^T2 :tdTomato bitransgenic mice, which harbor a tamoxifen-inducible tdTomato (tdTom) reporter for indelible labeling of newborn hippocampal DGCs. We exposed all mice to EtOH vapor or room air (Control) for 4 h/d from postnatal day (PND) 3 through PND 15. This paradigm resulted in a mean daily postexposure blood EtOH concentration of ~160 mg/dl. One cohort of neonatal mice received a single injection of tamoxifen at PND 2 and was sacrificed at either PND 16 or PND 50 to assess the impact of EtOH exposure on the production and long-term survival of dDGCs born during the early postnatal period. A second cohort of mice received daily injections of tamoxifen at PND 35 to 39 to label aDGCs and was exposed to SH or EE for 6 weeks prior to sacrifice.

RESULTS

Early postnatal EtOH exposure had no statistically significant effect on the production or survival of tdTom⁺ dDGCs, as assessed at PND 16 or PND 50. Early postnatal EtOH exposure also had no effect on the number of tdTom+ aDGCs under SH conditions. Furthermore, early postnatal EtOH exposure had no significant impact on the adult neurogenic response to EE.

CONCLUSIONS

Both early postnatal dentate neurogenesis and adult dentate neurogenesis, as well as the adult neurogenic response to EE, are surprisingly resistant to early postnatal EtOH vapor exposure in mice.

Genetic inactivation of synaptosomal-associated protein 25 (SNAP-25) in adult hippocampal neural progenitors impairs pattern discrimination learning but not survival or structural maturation of newborn dentate granule cells

Adult neurogenesis is necessary for proper cognition and behavior, however, the mechanisms that underlie the integration and maturation of newborn neurons into the pre-existing hippocampal circuit are not entirely known. In this study, we sought to determine the role of action potential (AP)-dependent synaptic transmission by adult-generated dentate granule cells (DGCs) in their survival and function within the existing circuitry. We used a triple transgenic mouse (NestinCreER^T2 :Snap25^fl/fl : tdTomato) to inducibly inactivate AP-dependent synaptic transmission within adult hippocampal progenitors and their progeny. Behavioral testing in a hippocampal-dependent A/B contextual fear-discrimination task revealed impaired discrimination learning in mice harboring SNAP-25-deficient adult-generated dentate granule cells (DGCs). Despite poor performance on this neurogenesis-dependent task, the production and survival of newborn DGCs was quantitatively unaltered in tamoxifen-treated NestinCreER^T2 :Snap25^fl/fl : tdTomato SNAP compared to tamoxifen-treated NestinCreER^T2 :Snap25^wt/wt : tdTomato control mice. Although SNAP-25-deficient adult DGCs displayed a small but statistically significant enhancement in proximal dendritic branching, their overall dendritic length and distal branching complexity was unchanged. SNAP-25-deficient newborn DGCs also displayed robust efferent mossy fiber output to CA3, with normal linear density of large mossy fiber terminals (LMTs). These studies suggest that AP-dependent neurotransmitter release by newborn DGCs is not essential for their survival or rudimentary structural maturation within the adult hippocampus.

Maternal circulating miRNAs that predict infant FASD outcomes influence placental maturation

Maternal gestational circulating microRNAs, predictive of adverse infant outcomes, including growth deficits, following prenatal alcohol exposure, contribute to placental pathology by impairing the EMT pathway in trophoblasts.

Prenatal alcohol exposure (PAE), like other pregnancy complications, can result in placental insufficiency and fetal growth restriction, although the linking causal mechanisms are unclear. We previously identified 11 gestationally elevated maternal circulating miRNAs (_HEamiRNAs) that predicted infant growth deficits following PAE. Here, we investigated whether these _HEamiRNAs contribute to the pathology of PAE, by inhibiting trophoblast epithelial–mesenchymal transition (EMT), a pathway critical for placental development. We now report for the first time that PAE inhibits expression of placental pro-EMT pathway members in both rodents and primates, and that _HEamiRNAs collectively, but not individually, mediate placental EMT inhibition. _HEamiRNAs collectively, but not individually, also inhibited cell proliferation and the EMT pathway in cultured trophoblasts, while inducing cell stress, and following trophoblast syncytialization, aberrant endocrine maturation. Moreover, a single intravascular administration of the pooled murine-expressed _HEamiRNAs, to pregnant mice, decreased placental and fetal growth and inhibited the expression of pro-EMT transcripts in the placenta. Our data suggest that _HEamiRNAs collectively interfere with placental development, contributing to the pathology of PAE, and perhaps also, to other causes of fetal growth restriction.

The brain-derived neurotrophic factor VAL68MET polymorphism modulates how developmental ethanol exposure impacts the hippocampus

Prenatal exposure to alcohol causes a wide range of deficits known as fetal alcohol spectrum disorders (FASDs). Many factors determine vulnerability to developmental alcohol exposure including timing and pattern of exposure, nutrition and genetics. Here, we characterized how a prevalent single nucleotide polymorphism in the human brain-derived neurotrophic factor (BDNF) gene (val66met) modulates FASDs severity. This polymorphism disrupts BDNF's intracellular trafficking and activity-dependent secretion, and has been linked to increased incidence of neuropsychiatric disorders such as depression and anxiety. We hypothesized that developmental ethanol (EtOH) exposure more severely affects mice carrying this polymorphism. We used transgenic mice homozygous for either valine (BDNFval/val ) or methionine (BDNFmet/met ) in residue 68, equivalent to residue 66 in humans. To model EtOH exposure during the second and third trimesters of human pregnancy, we exposed mice to EtOH in vapor chambers during gestational days 12 to 19 and postnatal days 2 to 9. We found that EtOH exposure reduces cell layer volume in the dentate gyrus and the CA1 hippocampal regions of BDNFmet/met but not BDNFval/val mice during the juvenile period (postnatal day 15). During adulthood, EtOH exposure reduced anxiety-like behavior and disrupted trace fear conditioning in BDNFmet/met mice, with most effects observed in males. EtOH exposure reduced adult neurogenesis only in the ventral hippocampus of BDNFval/val male mice. These studies show that the BDNF val66met polymorphism modulates, in a complex manner, the effects of developmental EtOH exposure, and identify a novel genetic risk factor that may regulate FASDs severity in humans.

Genetic inactivation of hypoxia inducible factor 1-alpha (HIF-1α) in adult hippocampal progenitors impairs neurogenesis and pattern discrimination learning

HIF-1α is a hypoxia-inducible protein that regulates many cellular processes, including neural stem cell maintenance. Previous work demonstrated constitutive stabilization of HIF-1α in neural stem cells (NSCs) of the adult mouse subventricular zone (SVZ) and hippocampal subgranular zone (SGZ). Genetic inactivation of NSC-encoded HIF-1α in the adult SVZ results in gradual loss of NSCs, but whether HIF-1α is required for the maintenance of SGZ hippocampal progenitors and adult hippocampal neurogenesis has not been determined. Here we tested the hypothesis that HIF-1α plays an essential role in the maintenance of adult hippocampal neurogenesis using Nestin-CreER^T2/R26R-YFP/Hif1a^fl/fl triple transgenic mice, in which HIF-1α was genetically inactivated in nestin⁺ hippocampal progenitors and their downstream progeny following tamoxifen exposure. We found that disruption of HIF-1α gene expression resulted in a marked 50% reduction of adult-generated dentate granule cells (DGCs) that was highly correlated with impaired hippocampal function, as assessed using two behavioral assays of pattern discrimination. These behavioral tests included the A-B contextual fear-conditioning task and the trial-unique, delayed nonmatching-to-location (TUNL) touch-screen operant chamber task. Our findings identify HIF-1α as a novel regulator of adult hippocampal neurogenesis under non-pathological conditions, and underscore the importance of neurogenesis for pattern discrimination learning.

Hippocampal deficits in neurodevelopmental disorders

Neurodevelopmental disorders result from impaired development or maturation of the central nervous system. Both genetic and environmental factors can contribute to the pathogenesis of these disorders; however, the exact causes are frequently complex and unclear. Individuals with neurodevelopmental disorders may have deficits with diverse manifestations, including challenges with sensory function, motor function, learning, memory, executive function, emotion, anxiety, and social ability. Although these functions are mediated by multiple brain regions, many of them are dependent on the hippocampus. Extensive research supports important roles of the mammalian hippocampus in learning and cognition. In addition, with its high levels of activity-dependent synaptic plasticity and lifelong neurogenesis, the hippocampus is sensitive to experience and exposure and susceptible to disease and injury. In this review, we first summarize hippocampal deficits seen in several human neurodevelopmental disorders, and then discuss hippocampal impairment including hippocampus-dependent behavioral deficits found in animal models of these neurodevelopmental disorders.

Long-term Reductions in the Population of GABAergic Interneurons in the Mouse Hippocampus following Developmental Ethanol Exposure

Developmental exposure to ethanol leads to a constellation of cognitive and behavioral abnormalities known as Fetal Alcohol Spectrum Disorders (FASDs). Many cell types throughout the central nervous system are negatively impacted by gestational alcohol exposure, including inhibitory, GABAergic interneurons. Little evidence exists, however, describing the long-term impact of fetal alcohol exposure on survival of interneurons within the hippocampal formation, which is critical for learning and memory processes that are impaired in individuals with FASDs. Mice expressing Venus yellow fluorescent protein in inhibitory interneurons were exposed to vaporized ethanol during the third trimester equivalent of human gestation (postnatal days 2-9), and the long-term effects on interneuron numbers were measured using unbiased stereology at P90. In adulthood, interneuron populations were reduced in every hippocampal region examined. Moreover, we found that a single exposure to ethanol at P7 caused robust activation of apoptotic neurodegeneration of interneurons in the hilus, granule cell layer, CA1 and CA3 regions of the hippocampus. These studies demonstrate that developmental ethanol exposure has a long-term impact on hippocampal interneuron survivability, and may provide a mechanism partially explaining deficits in hippocampal function and hippocampus-dependent behaviors in those afflicted with FASDs.

Effects of prenatal alcohol exposure (PAE): insights into FASD using mouse models of PAE

The potential impact of prenatal alcohol exposure (PAE) varies considerably among exposed individuals, with some displaying serious alcohol-related effects and many others showing few or no overt signs of fetal alcohol spectrum disorder (FASD). In animal models, variables such as nutrition, genetic background, health, other drugs, and stress, as well as dosage, duration, and gestational timing of exposure to alcohol can all be controlled in a way that is not possible in a clinical situation. In this review we examine mouse models of PAE and focus on those with demonstrated craniofacial malformations, abnormal brain development, or behavioral phenotypes that may be considered FASD-like outcomes. Analysis of these data should provide a valuable tool for researchers wishing to choose the PAE model best suited to their research questions or to investigate established PAE models for FASD comorbidities. It should also allow recognition of patterns linking gestational timing, dosage, and duration of PAE, such as recognizing that binge alcohol exposure(s) during early gestation can lead to severe FASD outcomes. Identified patterns could be particularly insightful and lead to a better understanding of the molecular mechanisms underlying FASD.

Prenatal Alcohol Exposure Leads to Enhanced Serine 9 Phosphorylation of Glycogen Synthase Kinase-3β (GSK-3β) in the Hippocampal Dentate Gyrus of Adult Mouse

BACKGROUND

The goal of this study was to evaluate the expression and serine 9 phosphorylation of glycogen synthase kinase (GSK-3β) within the adult hippocampal dentate gyrus (DG) in a preclinical mouse model of fetal alcohol spectrum disorders. GSK-3β is a multifunctional kinase that modulates many hippocampal processes affected by gestational alcohol, including synaptic plasticity and adult neurogenesis. GSK-3β is a constitutively active kinase that is negatively regulated by phosphorylation at the serine 9 residue.

METHODS

We utilized a well-characterized limited access "drinking-in-the-dark" paradigm of prenatal alcohol exposure (PAE) and measured p(Ser9)GSK-3β and total GSK-3β within adult DG by Western blot analysis. In addition, we evaluated the expression pattern of both p(Ser9)GSK-3β and total GSK-3β within the adult hippocampal dentate of PAE and control mice using high-resolution confocal microscopy.

RESULTS

Our findings demonstrate a marked 2.0-fold elevation of p(Ser9)GSK-3β in PAE mice, concomitant with a more moderate 36% increase in total GSK-3β. This resulted in an approximate 63% increase in the p(Ser9)GSK-3β/GSK-3β ratio. Immunostaining revealed robust GSK-3β expression within Cornu Ammonis (CA) pyramidal neurons, hilar mossy cells, and a subset of GABAergic interneurons, with low levels of expression within hippocampal progenitors and dentate granule cells.

CONCLUSIONS

These findings suggest that PAE may lead to a long-term disruption of GSK-3β signaling within the DG, and implicate mossy cells, GABAergic interneurons, and CA primary neurons as major targets of this dysregulation.

Prenatal Alcohol Exposure Affects Progenitor Cell Numbers in Olfactory Bulbs and Dentate Gyrus of Vervet Monkeys

Fetal alcohol exposure (FAE) alters hippocampal cell numbers in rodents and primates, and this may be due, in part, to a reduction in the number or migration of neuronal progenitor cells. The olfactory bulb exhibits substantial postnatal cellular proliferation and a rapid turnover of newly formed cells in the rostral migratory pathway, while production and migration of postnatal neurons into the dentate gyrus may be more complex. The relatively small size of the olfactory bulb, compared to the hippocampus, potentially makes this structure ideal for a rapid analysis. This study used the St. Kitts vervet monkey (Chlorocebus sabeus) to (1) investigate the normal developmental sequence of post-natal proliferation in the olfactory bulb and dentate gyrus and (2) determine the effects of naturalistic prenatal ethanol exposure on proliferation at three different ages (neonate, five months and two years). Using design-based stereology, we found an age-related decrease of actively proliferating cells in the olfactory bulb and dentate gyrus for both control and FAE groups. Furthermore, at the neonatal time point, the FAE group had fewer actively proliferating cells as compared to the control group. These data are unique with respect to fetal ethanol effects on progenitor proliferation in the primate brain and suggest that the olfactory bulb may be a useful structure for studies of cellular proliferation.

Prenatal alcohol exposure alters synaptic activity of adult hippocampal dentate granule cells under conditions of enriched environment

Prenatal alcohol exposure (PAE) results in fetal alcohol spectrum disorder (FASD), which is characterized by a wide range of cognitive and behavioral deficits that may be linked to impaired hippocampal function and adult neurogenesis. Preclinical studies in mouse models of FASD indicate that PAE markedly attenuates enrichment-mediated increases in the number of adult-generated hippocampal dentate granule cells (aDGCs), but whether synaptic activity is also affected has not been studied. Here, we utilized retroviral birth-dating coupled with whole cell patch electrophysiological recordings to assess the effects of PAE on enrichment-mediated changes in excitatory and inhibitory synaptic activity as a function of DGC age. We found that exposure to an enriched environment (EE) had no effect on baseline synaptic activity of 4- or 8-week-old aDGCs from control mice, but significantly enhanced the excitatory/inhibitory ratio of synaptic activity in 8-week-old aDGCs from PAE mice. In contrast, exposure to EE significantly enhanced the excitatory/inhibitory ratio of synaptic activity in older pre-existing DGCs situated in the outer dentate granule cell layer (i.e., those generated during embryonic development; dDGCs) in control mice, an effect that was blunted in PAE mice. These findings indicate distinct electrophysiological responses of hippocampal DGCs to behavioral challenge based on cellular ontogenetic age, and suggest that PAE disrupts EE-mediated changes in overall hippocampal network activity. These findings may have implications for future therapeutic targeting of hippocampal dentate circuitry in clinical FASD. © 2016 Wiley Periodicals, Inc.

Associative DNA methylation changes in children with prenatal alcohol exposure

Aim: Prenatal alcohol exposure (PAE) can cause fetal alcohol spectrum disorders (FASD). Previously, we assessed PAE in brain tissue from mouse models, however whether these changes are present in humans remains unknown. Materials & methods: In this report, we show some identical changes in DNA methylation in the buccal swabs of six children with FASD using the 450K array. Results: The changes occur in genes related to protocadherins, glutamatergic synapses, and hippo signaling. The results were found to be similar in another heterogeneous replication group of six FASD children. Conclusion: The replicated results suggest that children born with FASD have unique DNA methylation defects that can be influenced by sex and medication exposure. Ultimately, with future clinical development, assessment of DNA methylation from buccal swabs can provide a novel strategy for the diagnosis of FASD.

Amphetamine sensitization and cross-sensitization with acute restraint stress: impact of prenatal alcohol exposure in male and female rats

RATIONALE

Individuals with fetal alcohol spectrum disorder (FASD) are at increased risk for substance use disorders (SUD). In typically developing individuals, susceptibility to SUD is associated with alterations in dopamine and hypothalamic-pituitary-adrenal (HPA) systems, and their interactions. Prenatal alcohol exposure (PAE) alters dopamine and HPA systems, yet effects of PAE on dopamine-HPA interactions are unknown. Amphetamine-stress cross-sensitization paradigms were utilized to investigate sensitivity of dopamine and stress (HPA) systems, and their interactions following PAE.

METHODS

Adult Sprague-Dawley offspring from PAE, pair-fed, and ad libitum-fed control groups were assigned to amphetamine-(1-2 mg/kg) or saline-treated conditions, with injections every other day for 15 days. Fourteen days later, all animals received an amphetamine challenge (1 mg/kg) and 5 days later, hormones were measured under basal or acute stress conditions. Amphetamine sensitization (augmented locomotion, days 1-29) and cross-sensitization with acute restraint stress (increased stress hormones, day 34) were assessed.

RESULTS

PAE rats exhibited a lower threshold for amphetamine sensitization compared to controls, suggesting enhanced sensitivity of dopaminergic systems to stimulant-induced changes. Cross-sensitization between amphetamine (dopamine) and stress (HPA hormone) systems was evident in PAE, but not in control rats. PAE males exhibited increased dopamine receptor expression (medial prefrontal cortex (mPFC)) compared to controls.

CONCLUSIONS

PAE alters induction and expression of sensitization/cross-sensitization, as reflected in locomotor, neural, and endocrine changes, in a manner consistent with increased sensitivity of dopamine and stress systems. These results provide insight into possible mechanisms that could underlie increased prevalence of SUD, as well as the impact of widely prescribed stimulant medications among adolescents with FASD.

Prenatal alcohol exposure alters expression of neurogenesis-related genes in an ex vivo cell culture model

Prenatal alcohol exposure can lead to long-lasting changes in functional and genetic programs of the brain, which may underlie behavioral alterations seen in Fetal Alcohol Spectrum Disorder (FASD). Aberrant fetal programming during gestational alcohol exposure is a possible mechanism by which alcohol imparts teratogenic effects on the brain; however, current methods used to investigate the effects of alcohol on development often rely on either direct application of alcohol in vitro or acute high doses in vivo. In this study, we used our established moderate prenatal alcohol exposure (PAE) model, resulting in maternal blood alcohol content of approximately 20 mM, and subsequent ex vivo cell culture to assess expression of genes related to neurogenesis. Proliferating and differentiating neural progenitor cell culture conditions were established from telencephalic tissue derived from embryonic day (E) 15-17 tissue exposed to alcohol via maternal drinking throughout pregnancy. Gene expression analysis on mRNA derived in vitro was performed using a microarray, and quantitative PCR was conducted for genes to validate the microarray. Student's t tests were performed for statistical comparison of each exposure under each culture condition using a 95% confidence interval. Eleven percent of genes on the array had significantly altered mRNA expression in the prenatal alcohol-exposed neural progenitor culture under proliferating conditions. These include reduced expression of Adora2a, Cxcl1, Dlg4, Hes1, Nptx1, and Vegfa and increased expression of Fgf13, Ndn, and Sox3; bioinformatics analysis indicated that these genes are involved in cell growth and proliferation. Decreased levels of Dnmt1 and Dnmt3a were also found under proliferating conditions. Under differentiating conditions, 7.3% of genes had decreased mRNA expression; these include Cdk5rap3, Gdnf, Hey2, Heyl, Pard6b, and Ptn, which are associated with survival and differentiation as indicated by bioinformatics analysis. This study is the first to use chronic low to moderate PAE, to more accurately reflect maternal alcohol consumption, and subsequent neural progenitor cell culture to demonstrate that PAE throughout gestation alters expression of genes involved in neural development and embryonic neurogenesis.

Prenatal alcohol exposure alters p35, CDK5 and GSK3β in the medial frontal cortex and hippocampus of adolescent mice

Fetal alcohol spectrum disorders (FASDs) are the number one cause of preventable mental retardation. An estimated 2-5% of children are diagnosed as having a FASD. While it is known that children prenatally exposed to alcohol experience cognitive deficits and a higher incidence of psychiatric illness later in life, the pathways underlying these abnormalities remain uncertain. GSK3β and CDK5 are protein kinases that are converging points for a vast number of signaling cascades, including those controlling cellular processes critical to learning and memory. We investigated whether levels of GSK3β and CDK5 are affected by moderate prenatal alcohol exposure (PAE), specifically in the hippocampus and medial frontal cortex of the adolescent mouse. In the present work we utilized immunoblotting techniques to demonstrate that moderate PAE increased hippocampal p35 and β-catenin, and decreased total levels of GSK3β, while increasing GSK3β Ser9 and Tyr216 phosphorylation. Interestingly, different alterations were seen in the medial frontal cortex where p35 and CDK5 were decreased and increased total GSK3β was accompanied by reduced Tyr216 of the enzyme. These results suggest that kinase dysregulation during adolescence might be an important contributing factor to the effects of PAE on hippocampal and medial frontal cortical functioning; and by extension, that global modulation of these kinases may produce differing effects depending on brain region.